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Checked the PVC valve and had tape stuck over the end where I'd tried to fatten the valve into the grommet.
Replaced valve anyway

Bought a cheap Endoscope off ebay but couldn't get a clear view of the cylinders.
Tried viewing into the inlet manifold port runners and again couldn't really see any definitive detail.

Made a smoke machine with a stainless chamber & a small compressor
Pumped several smoke pellets into the crankcase through the rocker cover.
had smoke forcing its way out of the dipstick hole
I could NOT see any smoke in the manifold runners which I suppose is good in a way.
Certainly ticks the box the manifold is sealing.

Resealed the AIR tube plugs in the exhaust manifolds with epoxy metal and replaced.

Started the car and the RHS O2 started to drop after a minute or two.
Vacuum gauge was pretty stable.
Tailpipes were smoking white quite a lot, it's freezing and snowing here.
So I let it warm up and did a water decoke into the inlet manifold.
Used about 1.5 pints over several minutes.
The O2's and wideband all flatlined.
Retarded the timing with EEHack (Thanks Steveo) to pump heat into the exhausts.

After another 5 minutes or so the O2's came back on line
Wideband followed suit.
The smoke has cleared up from the tailpipe.
The smoke from the rear of the inlet manifold also had cleared up so PCV seems to be working now.

Car is idling pretty sweet.
The RH O2 sensor is now consistanly reading higher than the left as i'd fattened it up slightly which it has never done before
and the wideband reading was also more stable around 12.5

I'm just waiting for new O2 sensors and plugs to arrive.
I will monitor this for a while before changing anything over and see what develops.

Update

OK guys, quick update on this.
I feel pretty certain that
a) the injectors are OK
b) the manifold is NOT leaking from underneath.
c) O2's were/are fine.

O2's arrived so i changed them out to rule them out.
I have a new set of plugs to go in but just cleaned the previous ones up for now.

I've been through the entire bin and compared it to the original Stock Z28 M6 Bin.
I put all the Closed loop delays and CORRCL values back to stock.
Individual cylinder fuel trims and Timing.
Injectors are currently sized at 41lb not the 42 they are rated at. Only 2-3% off.

The car ran much nicer and 1 could take the clutch up in first at idle and the car would roll 5-7mph without me losing any teeth with the surge.
On the initial warmup I've raised Open Loop AFR Target starting at around 14.1 but the wideband is reading 10.5 to 11
I don't know how I can raise that up much more?

The O2's drop at exactly the same point as the last 3 logs, 49 Degrees C to 56 Degrees C
The Injector constants don't change much, The LHS O2 bounces around, the RHS hits the floor. I suspect this could be plugs, fouling from too rich at startup maybe?
By 56 degrees C the O2's both recover and read a steady 900mv until CL at 60 degrees C.

Used Steveo's Trimalyzer to get the VE tables back into shape. They are starting to push Low 90's%.
Some tweaks to the Individual Cylinder Fuel trims is bringing the BLM's back into shape, within 121-129
The car is currently happier now than previously in CL and the Wideband is much closer to the req AFR the previously.

Other than using an IR temp probe or 4 Widebands is there any better way to balance the fuel trims.
That was the reason I was asking about identifying the cylinder in the log with the Cyl ID.
I guess there aren't any messages available to trim cylinders individually?

Since it's a relatively easy procedure I'd be interested to see if you swapped your four right / even bank injectors for your four odd bank injectors, if the flatlined O2 follows the injectors.

I too would be interested in developing a more scientific yet practical approach to individual cylinder trims. Reading the exhaust temps with IR feels like an exercise in futility. I've been searching for economically feasible thermocouples and RTDs and have been coming up empty. I was intending to use 1-wire DS18S20 sensors until I refreshed my memory with the datasheet and recalled they were rated only to 257F, not C.

Since it's a relatively easy procedure I'd be interested to see if you swapped your four right / even bank injectors for your four odd bank injectors, if the flatlined O2 follows the injectors.

I've just been back through all my earlier logs to when I installed the injectors and they were doing it back then 49-55 Deg C
I had started using EEHack at that point so need to fire up data master to see earlier logs with the other injectors.

I think i'm going to bin these injectors off & get some new ones if anyone has any good suggestions.

I've set the voltage offsets up as per the calcs i was given.
This got the PW up into the 2ms range for idle but the VE tables went to pot.
As I played with VE the tables keep maxing out and I'm back lying to the system with 38 for the INJ Constant with 42's in.

The RHS is going progresivly leaner the more I play.
When the motor is pig rich it's fine.
As I lean it back out it's less happy. It buzzes and vibes more.

I was going to play & swap them over or piss about with the older ones but then I've just got to waste more time doing that again so i'm biting the bullet and get another set.

Update

The new injectors have arrived and i'm still dialing them in.
The car is definately feeling different.
The low speed surge is back but the current .bin is heavly copied from the LT4 .bin i have rather than my previous setup.

It feels to have more power up top.
It was spinning the wheels in third around 78mph without much effort.
The fastest RPM i wound it to was 5500 at 67mph.
It felt higher but the roads are just above freezing.

The idle isn't as sweet yet as before.
Fueling is still a bit off on the Individual injector settings, but the VE table is a much smoother shape and has a much wider spread of values than previously.

So far the VE tables are settling down nicely using Steveo's Trimalyzer, so a happy camper.

Originally Posted by kur4o

If you have ls1 style injector data you can try my newest patch.

Maybe when i get these up to par.
Is that the fixed fuel pressure one?
I presume i could extrapolate the data from the other Fuel pressure data?

Would that work by disconnecting the vac line to the fuel regulator?
What's your opinion on the Aeromotive one as I was looking at them this last week esp. with a fuel gauge.
How good is the stock unit (23 years old now)?
What sort of power would the stock fuel pump be rated for?

I think I remember reading Steveo damping the map sensor response down to smooth the pulses to the Fuel regulator, Any thoughts on that?

Originally Posted by kur4o

What is that lt4 bin you have? As far as I know lt4 was introduced 1996.

That was in the recent attachment on the LT1 diss zip.
I can't remember who posted it.
I just picked bits of the LT4 tables out that I liked compared to the stock Z28 vs my recent tunes.

I am glad your getting closer to the perfect tune.
I only idle the car twice with the regulator so don`t have any usable data how good it is.
I put aeromotive 13107 since I have it from a long time. It is marked as 07/2011 unit, so shouldn`t give any real hints of the unit produced today.
Stock one looked pretty good and as long it keeps constant 3 bar pressure I wouldn`t bother replacing it.
I have plans to bump the pressure to 4 bars and installed it since the rail was off anyway.
I read somewhere that stock pump is good for 450hp, but I am not sure it will handle increased 4 bar pressure.

Patch will work with vacuum disconnected and constant fuel rail pressure.
You will need to have a good injector data though.

I checked a company called Injector Dynamics. They seem to provide good data, but are really expensive.
If you know how much hp you are making you can calculated the size of injectors needed. Bigger doesnt always mean better.